Clinical pharmacokinetics of oral cephalosporins

Cefpodoxime proxetil as a therapeutic option in switching therapy for infective endocarditis in children: case reports and literature review

Infective endocarditis (IE) is uncommon in children, affecting predominantly subjects with congenital heart disease (CHD) and patients with indwelling central lines. The principles of antibiotic treatment in paediatric population are similar to those in adults. Prolonged intravenous administration of bactericidal rather than bacteriostatic agents is preferred. Outpatient intravenous therapy after initial treatment in the hospital may be considered only in selected patients. Partial oral treatment has been described in cases of left-sided, uncomplicated IE caused by common pathogens in adult patients. There are no guidelines or trials in paediatric population regarding switching therapy from intravenous to oral route. We present two cases of IE in children caused by uncommon pathogenic bacteria (Abiotrophia defectiva and Haemophilus parainfluenzae) successfully treated with oral third-generation cephalosporin - cefpodoxime proxetil after initial intravenous therapy. This paper provides observations on different therapeutic approach for IE in children as well as another potential use of cefpodoxime proxetil.

Novel carbapenem antibiotics for parenteral and oral applications: in vitro and in vivo activities of 2-aryl carbapenems and their pharmacokinetics in laboratory animals

SM-295291 and SM-369926 are new parenteral 2-aryl carbapenems with strong activity against major causative pathogens of community-acquired infections such as methicillin-susceptible Staphylococcus aureus, Streptococcus pneumoniae (including penicillin-resistant strains), Streptococcus pyogenes, Enterococcus faecalis, Klebsiella pneumoniae, Moraxella catarrhalis, Haemophilus influenzae (including β-lactamase-negative ampicillin-resistant strains), and Neisseria gonorrhoeae (including ciprofloxacin-resistant strains), with MIC(90)s of ≤ 1 μg/ml. Unlike tebipenem (MIC(50), 8 μg/ml), SM-295291 and SM-369926 had no activity against hospital pathogens such as Pseudomonas aeruginosa (MIC(50), ≥ 128 μg/ml). The bactericidal activities of SM-295291 and SM-369926 against penicillin-resistant S. pneumoniae and β-lactamase-negative ampicillin-resistant H. influenzae were equal or superior to that of tebipenem and greater than that of cefditoren. The therapeutic efficacies of intravenous administrations of SM-295291 and SM-369926 against experimentally induced infections in mice caused by penicillin-resistant S. pneumoniae and β-lactamase-negative ampicillin-resistant H. influenzae were equal or superior to that of tebipenem and greater than that of cefditoren, respectively, reflecting their in vitro activities. SM-295291 and SM-369926 showed intravenous pharmacokinetics similar to those of meropenem in terms of half-life in monkeys (0.4 h) and were stable against human dehydropeptidase I. SM-368589 and SM-375769, which are medoxomil esters of SM-295291 and SM-369926, respectively, showed good oral bioavailability in rats, dogs, and monkeys (4.2 to 62.3%). Thus, 2-aryl carbapenems are promising candidates that show an ideal broad spectrum for the treatment of community-acquired infections, including infections caused by penicillin-resistant S. pneumoniae and β-lactamase-negative ampicillin-resistant H. influenzae, have low selective pressure on antipseudomonal carbapenem-resistant nosocomial pathogens, and allow parenteral, oral, and switch therapies.

New semiphysiological absorption model to assess the pharmacodynamic profile of cefuroxime axetil using nonparametric and parametric population pharmacokinetics

Cefuroxime axetil is widely used to treat respiratory tract infections. We are not aware of a population pharmacokinetic (PK) model for cefuroxime axetil. Our objectives were to develop a semiphysiological population PK model and evaluate the pharmacodynamic profile for cefuroxime axetil. Twenty-four healthy volunteers received 250 mg oral cefuroxime as a suspension after a standardized breakfast. Liquid chromatography-tandem mass spectrometry was used for drug analysis, NONMEM and S-ADAPT (results reported) were used for parametric population PK modeling, and NPAG was used for nonparametric population PK modeling. Monte Carlo simulations were used to predict the duration for which the non-protein-bound-plasma concentration was above the MIC (fT(>MIC)). A model with one disposition compartment, a saturable and time-dependent drug release from the stomach, and fast drug absorption from the intestine yielded precise (r > 0.992) and unbiased curve fits and an excellent predictive performance. The apparent clearance was 21.7 liters/h (19.8% coefficient of variation [CV]) and the volume of distribution 38.7 liters (18.3% CV). Robust (>or=90%) probabilities of target attainment (PTAs) were achieved by 250 mg cefuroxime given every 12 h (q12h) or q8h for MICs of <or=0.375 mg/liter or <or=0.5 mg/liter, respectively, for the bacteriostasis target fT(>MIC) of >or=40% and for MICs of <or=0.094 mg/liter or <or=0.375 mg/liter, respectively, for the near-maximal-killing target fT(>MIC) of >or=65%. For the >or=40% fT(>MIC) target, the PTAs for 250 mg cefuroxime q12h were >or=97.8% for Streptococcus pyogenes and penicillin-susceptible Streptococcus pneumoniae. Cefuroxime at 250 mg q12h or q8h achieved PTAs below 73% or 92%, respectively, for Haemophilus influenzae, Moraxella catarrhalis, and penicillin-intermediate S. pneumoniae for susceptibility data from various countries. Depending on the MIC distribution, 250 mg oral cefuroxime q8h instead of q12h should be considered, especially for more-severe infections that require near-maximal killing by cefuroxime.

Ontogeny of drug elimination by the human kidney

Renal clearance is an important route of drug elimination. While during the neonatal period there is minimal glomerular filtration and active tubular secretion of drugs, there is a well-described rapid development in these processes in the post-neonatal period. A less appreciated fact is that during toddlerhood, there is an "overshoot" of the glomerular filtration rate (GFR) well above the levels encountered in older children and adults, and there is an early achievement of adult levels in active drug secretion, which stays at a plateau throughout childhood and adulthood with an "overshoot" in toddlers due to specific transport mechanisms. This phenomenon leads to dose requirements for renally excreted drugs in this age group being, on a per-kilogram basis, much larger than in adults. This review discusses the mechanisms related to renal ontogeny in drug handling.

The influence of pH, temperature and buffers on the degradation kinetics of cefetamet pivoxil hydrochloride in aqueous solutions

The first-order hydrolysis kinetics of cefetamet pivoxil (CP) were investigated as a function of pH, temperature and buffers. The degradation was followed by HPLC. Buffer catalysis was observed in acetate and phosphate buffers. The pH-rate profiles for hydrolysis of cefetamet pivoxil were obtained at 333, 343, 353 and 363K. The pH-rate expression was k(pH)=kH+aH+ + kH2OkOH-aOH-, where kH+ and kOH- are the second-order rate constants (mol(-1)ls(-1)) for hydrogen ion activity and for hydroxyl ion activity respectively, and kH2O is the pseudo-first-order rate constant (s(-1)) for spontaneous reaction under the influence of water. The pH-rate profile was characteristically U-shaped. Maximum stability was observed in the pH region from 3 to 5.

Efficacy and safety of short course (5-day) moxifloxacin vs 7-day ceftriaxone in the treatment of acute exacerbations of chronic bronchitis (AECB)

The aim of this multicenter, open, randomized study was to compare the efficacy and tolerability of a 5-day treatment course with oral moxifloxacin (MXF) vs a 7-day course with i.m. ceftriaxone (CRO) in 476 patients with acute exacerbations of chronic bronchitis (AECB), and to conduct a cost minimization analysis of the two treatments from the perspectives of both the Italian National Health Service (INHS) and society. The study was conducted in Italy. Clinical success rates at test-of-cure in the 423 patients of the PP (Per Protocol) population (primary efficacy parameter) were 90.6% and 89.0% for MXF and CRO, respectively. Statistical non-inferiority of MXF vs CRO was confirmed. Similar results were found between study drugs on the secondary efficacy parameters, including success at end-of-treatment (95.3% for MXF vs 92.9% for CRO), success at test-of-cure in bacteriologically-positive patients (94.1% vs 90.7%) and eradication/presumed eradication rates (91.7% vs 93.3%). ITT (Intention-to-Treat) analysis confirmed these data. There was a low incidence of adverse events (10.8% vs 9.1%). During a 6-month follow-up period, relapse rates were lower for MXF vs CRO (23.3% vs 28.3%; p > .05). Compared with CRO, MXF was associated with cost savings per patient ranging from Euro226.57 (INHS perspective) to Euro448.23 (societal perspective), with lower hospitalization rate the major variable contributing to reduced costs. MXF appears to be an ideal candidate for AECB treatment.

Cefuroxime axetil: an updated review of its use in the management of bacterial infections

Cefuroxime axetil, a prodrug of the cephalosporin cefuroxime, has proven in vitro antibacterial activity against several gram-positive and gram-negative organisms, including those most frequently associated with various common community-acquired infections. In numerous randomised, controlled trials, 5 to 10 days' treatment with oral cefuroxime axetil (250 or 500 mg twice daily) was an effective treatment in patients with upper (URTI) and lower respiratory tract infections (LRTI) as assessed by clinical and bacteriological criteria. The drug was as effective as several other cephalosporins, quinolones, macrolides and amoxicillin/clavulanic acid. Shorter courses (5 to 10 days') of cefuroxime axetil were at least as effective as a 10 day course. Furthermore, sequential therapy with intravenous cefuroxime (750 mg 2 or 3 times daily for 2 to 5 days) followed by oral cefuroxime axetil (500 mg twice daily for 3 to 8 days) proved an effective treatment in adult patients with community-acquired pneumonia (CAP). This approach provided similar efficacy to intravenous ampicillin/sulbactam followed by oral amoxicillin/clavulanic acid, a full parenteral course of cefuroxime, or intravenous then oral azithromycin or clarithromycin. Additionally, cefuroxime axetil was an effective treatment in patients with genitourinary, skin and soft-tissue infections, and erythema migrans associated with early stage Lyme disease. The drug is well tolerated by adult and paediatric patients, with adverse effects that are consistent with those of other cephalosporins. The majority of adverse events (primarily gastrointestinal disturbances) were mild to moderate in intensity and reversible upon discontinuation of treatment, with very few serious adverse events reported.

CONCLUSIONS

Cefuroxime axetil is a broad spectrum antibacterial agent with a pharmacokinetic profile that permits convenient twice-daily administration. The drug is an effective and well tolerated treatment in patients with various infections, including otitis media, pharyngitis, sinusitis, CAP and acute exacerbations of chronic bronchitis. Cefuroxime axetil proved effective as a component of intravenous/oral sequential therapy in the treatment of CAP, although there are currently no dosage recommendations available for this regimen in some countries. Cefuroxime axetil may be considered as an empirical therapy for a range of community-acquired infections, including those in which beta-lactamase-producing strains of common respiratory pathogens are identified as the causative organisms. In an era of rapidly emerging bacterial resistance, empirical treatment with bacterial agents, potentially preventing the emergence of bacterial resistance to agents such as cefuroxime axetil may ensure the appropriate use of newer antibacterial agents, potentially preventing the emergence of bacterial resistance to these newer drugs.

Cefpodoxime proxetil: a review of its use in the management of bacterial infections in paediatric patients

Cefpodoxime proxetil is an oral third generation cephalosporin with a broad spectrum of antibacterial activity. The drug has in vitro activity against many common Gram-positive and Gram-negative pathogens associated with common paediatric infections, making the drug a useful option for empirical therapy. In randomised controlled trials conducted in children with acute otitis media, oral cefpodoxime proxetil 8 to 10 mg/kg/day (usually administered in 2 divided doses) for 5 to 10 days was at least as effective as standard regimens of amoxicillin/ clavulanic acid, cefixime, cefuroxime axetil or cefaclor as assessed by either clinical or bacteriological criteria. Cefpodoxime 8 to 10 mg/kg/day (administered in 2 divided doses) for 5 to 10 days was at least as effective as standard 10-day regimens of penicillin V in the treatment of children with pharyngitis and/or tonsillitis. Significant differences in favour of cefpodoxime proxetil were demonstrated in terms of clinical (1 study) and bacteriological (2 studies) criteria. The clinical efficacy of 5 days of treatment with cefpodoxime proxetil is similar to that of 10 days of treatment with penicillin V. In children with lower respiratory tract infections (primarily pneumonia), clinical and bacteriological efficacy rates achieved with cefpodoxime proxetil treatment were similar to those produced by cefuroxime axetil or amoxicillin/clavulanic acid in randomised controlled trials. Cefpodoxime proxetil also demonstrated clinical efficacy in paediatric patients with skin and soft tissue infections. In randomised studies that included both adults and children with a variety of infections (e.g. abscess, atheroma, furuncle and carbuncle, infected wounds, cellulitis), cefpodoxime proxetil showed efficacy similar to that of cefuroxime axetil or cefaclor. Cefpodoxime proxetil is well tolerated by paediatric patients, with adverse events (primarily gastrointestinal tract disturbances and skin rashes) that are consistent with those reported for other oral cephalosporins.

CONCLUSION

Cefpodoxime proxetil is a third generation cephalosporin with a broad spectrum of antibacterial activity and a favourable pharmacokinetic profile which allows twice-daily administration. It is generally well tolerated and demonstrates good bacteriological and clinical efficacy in paediatric patients with various infectious diseases, including acute otitis media, tonsillitis and/or pharyngitis. Based on these characteristics, cefpodoxime proxetil is a suitable option for the treatment of paediatric patients with various common bacterial infections.

The cephalosporins

The cephalosporins are a large group of related beta-lactam antimicrobial agents. Favorable attributes of the cephalosporins include low rates of toxicity, relatively broad spectrum of activity, and ease of administration. Various cephalosporins are effective for treatment of many conditions, including pneumonia, skin and soft tissue infections, bacteremia, and meningitis. Differences among the numerous cephalosporin antimicrobial agents are sometimes subtle; however, an understanding of these differences is essential for optimal use of these agents. As a result of widespread use of cephalosporins, bacterial resistance to these drugs is increasingly common. New, fourth-generation agents (such as cefepime) offer an alternative for the treatment of infections caused by some drug-resistant microorganisms.

Stability of cephalosporin prodrug esters in human intestinal juice: implications for oral bioavailability

The levels of degradation of cefetamet pivoxil (CAT), cefuroxime axetil (CAE), and cefpodoxime proxetil (CPD) in 0.6 M phosphate buffer (pH 7.4) and human intestinal juice (pH 7.4) at 37 degreesC over 24 h were compared. Significant differences in the time courses of degradation and in the patterns of degradation products were observed. (i) The relative proportions of the Delta2- and Delta3-cephalosporins were roughly reversed in the two incubation media. In phosphate buffer, the major degradation product was the Delta2-cephalosporin (CAT = 61%; CAE = 74%; CPD = 85%), while in intestinal juice it was the Delta3-cephalosporin (CAT = 86%; CAE = 75%; CPD = 87%). (ii) Generally, the degradation of the prodrug esters progressed faster in intestinal juice than in phosphate buffer (e.g., for CAT the half-lives [t1/2s] were 0.78 and 4.3 h, respectively). (iii) The two diastereoisomers of CAE and CPD were degraded at different rates in intestinal juice (for the CAE diasteroisomers, t1/2s = 0.37 and 0.93 h; for the CPD diastereoisomers, t1/2s = 0.18 and 0.98 h) but were degraded at similar rates in phosphate buffer (for the CAE diastereoisomers, t1/2 = 1.6 h; for the CPD t1/2 diastereoisomers, = 2.2 h). It is concluded that (i) the Delta2 isomerization does not significantly affect the bioavailability of prodrug esters since enzymatic hydrolysis in the intestinal fluid proceeds mainly to the active Delta3-cephalosporin and (ii) the high degree of stereoselectivity of the enzymatic ester hydrolysis should make it possible to increase the bioavailabilities of certain prodrug esters (CAE, CPD) by using the more stable diasterioisomer.

Determination of third-generation cephalosporins by high-performance liquid chromatography in connection with pharmacokinetic studies

The third-generation cephalosporins are semisynthetic beta-lactam antibiotics, including several oral and parental agents with extended activity against Gram-negative pathogens. They are generally determined either by microbiological techniques or by high-performance liquid chromatography (HPLC). The major drawback or bioassays is the lack of specificity, especially when a biotransformation of the cephalosporin molecule leads to active metabolites, or when the antibacterial therapy is based on association with drugs. Thus, for many years, numerous reversed-phase HPLC procedures have been proposed to overcome these difficulties. This review presents different HPLC methods proposed for the quantification in biological fluids of fourteen third-generation cephalosporins, ranged between parenteral and oral compounds. The sensitivity and specificity of these chromatographic procedures are discussed with regard to the pharmacokinetic properties of the antibiotics studied.

Penetration of cefetamet pivoxil and cefuroxime axetil into the maxillary sinus mucosa at steady state

The penetration of cefetamet and cefuroxime into the maxillary sinus mucosa after the administration of cefetamet pivoxil and cefuroxime axetil was investigated in patients undergoing elective surgery of the maxillary sinus. A total of 27 patients, 13 for cefetamet pivoxil and 14 for cefuroxime axetil, ranging from 15 to 70 years of age participated in this study. Each patient received three oral doses of either one tablet of cefetamet pivoxil (500 mg of GLOBOCEF) or two film tablets of cefuroxime axetil (125 and 250 mg of ZINAT) every 12 h. Sinus mucosa tissue samples were removed during surgery at times ranging from 2 to 4.5 h after the last oral administration. Blood samples were collected before drug administration, 2 h after the first and third doses, and concomitantly with tissue sample collection during surgery. All samples were analyzed by high-performance liquid chromatography. The concentrations of cefetamet and cefuroxime in plasma samples measured concomitantly with those in tissue samples ranged between 0.83 and 4.5 micrograms/ml for cefetamet and 0.59 and 3 micrograms/ml for cefuroxime. The mean tissue-to-plasma ratios calculated with reference to total (bound plus unbound) plasma drug concentrations were 0.60 (range, 0.52 to 0.77) for cefetamet (n = 4) and 0.38 (range, 0.28 to 0.44) for cefuroxime (n = 6). Both drugs seem to penetrate freely and easily into the sinus mucosa. The antibacterial activities of cefetamet pivoxil and cefuroxime axetil in cases of sinusitis therefore depend mainly on their achieved active plasma drug concentrations and their intrinsic activities in inhibiting the causative organism(s).

Influence of maturation and growth on cefetamet pivoxil pharmacokinetics: rational dosing for infants

The pharmacokinetics of intravenous (i.v.) cefetamet and the bioavailability of oral cefetamet pivoxil in infants aged 3.5 to 17.3 months who were hospitalized for urological surgery were characterized. The absorption of cefetamet pivoxil administered in a syrup formulation was 38 +/- 19% (n = 5) for infants, which was comparable to values observed for children and adults. The plasma half-life of i.v. cefetamet was 3.03 +/- 0.96 h (mean +/- standard deviation; n = 20) in the infants. This was not different from the value observed for normal adult subjects but was longer than that reported for children aged 3 to 12 years. Urinary recovery of cefetamet after i.v. administration to infants was 63.4 +/- 17.7% (n = 16), which was less than the 80% recovery found in older children and adults. The steady-state volume of distribution was 399 +/- 116 ml/kg of body weight. It was comparable in size and showed the same dependence on body weight as it did in children and adults. The mean systemic clearance per kilogram of body weight in the infants was lower than that in children and adults, apparently because of immaturity of clearance processes. A model that accounted for maturation and growth with increasing age was developed for the clearance. On the basis of this model, the clearance capacity increased from birth to 5 years by a factor of 4.5 because of maturation. Maturation progressed exponentially, with a half-life of 14 months. This model was used to develop dosing regimen guidelines for pediatric patients aged 3.5 months and older.